The development of nano and non-toxic materials have attracted great attention of material scientists due to their fascinating characteristics, enabling synthesis of multifunctional materials and addressing the challenges of solving problem of utilization of toxic and non-toxic industrial wastes for making value added materials useful for broad application spectrum.
Brine sludge is an industrial waste generated in the chloralkali industry. The chloralkali process is the main process for manufacturing of caustic soda and chlorine production all over the world. In India a total of almost 36 chloralkali plants are in operational form. Brine mud generation is around 30 kg per ton caustic soda in India, which is more than double the international average. To achieve total utilization of this brine sludge, no processes have been developed to date.
In the chloralkali industry, the production of NaOH and chlorine is carried out by the electrolysis of purified brine solution, i.e. 30% sodium chloride solution, and the process of purification of impure brine solution involves removal of sulphate and chloride salts of magnesium and potassium. Removal of sulphate species is carried out by adding barium carbonate, which is expensive and leads to the generation of toxic brine sludge waste containing barium sulphate. Further removal of chloride species is carried out by adding sodium carbonate leading to the generation of brine sludge containing calcium carbonate and magnesium hydroxide. The generated brine sludge waste is dumped into landfills, which contains barium sulphate, calcium carbonate, magnesium hydroxide, sodium chloride, clay and toxic elements like chromium, zinc, copper and vanadium, therefore posing environmental threat. Therefore, there is an urgent need to provide a process which converts toxic brine sludge waste into non-toxic form.
Reference may be made to the article Utilization of Brine Sludge in Nonstructural Building components: A Sustainable Approach, by Mridul Garg and Aakanksha Pundir in Journal of Waste Management, vol.2014, Article ID 389316, 7 pages, wherein brine sludge has been utilized for making low value items like bricks and paver blocks using conventional cement and fly ash. However, the drawbacks of the cited process are that the brine sludge has been used in conjunction with cement and fly ash for making only paver blocks and bricks with only 35%, i.e. minimal utilization, of brine sludge. Thus, the problem of utilization of 65% brine sludge still remains. Further, the toxic elements present in the brine sludge have only been stabilized in cement matrix without forming any chemical linkages with the toxic elements. Hence, there is no assurance of non-leaching of the toxic elements in the environment from the prepared bricks and paver blocks. Since the brine sludge has not been converted into nano size and in functionalized form, it poses limited application in making paver blocks and brick materials only. Additionally, the developed process is based on the age old concept of stabilization of industrial waste into low value added materials to somehow address the problem of disposal and utilization of waste. The process does not teach the use of any advance synthesis technology for making value added materials so as to meet the challenges and stringent rules and regulations of environmental protection acts to address the problem of utilization of industrial toxic wastes.
Reference may be made to the patent publication No. CN101823738A, wherein a method for co-production of fine calcium carbonate and sodium silicate during preparation of light magnesium carbonate by chloralkali brine sludge has been reported. However, the drawbacks of the process are that it involves multiple steps, is energy intensive, and does not utilize the brine sludge in totality, thereby posing threat to the environment.
Reference may be made to the patent publication No. CN101823822A, wherein hydrochloric acid is used for purifying precipitates of calcium carbonate and calcium sulphate left after the production of light magnesium carbonate. However, the drawbacks of the process reside in the fact that it involves multiple steps, is energy and equipment intensive, and does not utilize the brine sludge in totality, thereby posing threat to the environment.
Further, from the reported prior art it is evident that total utilization of brine sludge for making highly value added advance materials has not been pursued seriously. From the hitherto reported prior art and based on the drawbacks of the known processes, the various issues that need to be addressed and problems to be solved for utilization of toxic brine sludge are summarized here as follows:                The brine sludge is toxic and therefore, it creates threat to the environment by remaining unutilized.        Since the brine sludge contains very useful and expensive chemical compounds such as barium sulphate, magnesium hydroxide and calcium carbonate, it can find application in making highly value added and functionalized materials such as radiation shielding materials, geo polymeric materials, and advanced chemically designed composite (ACDC) materials by utilizing unique characteristics of chemical compounds inherently present therein.        Brine sludge waste is available in micron size particles, thus restricting its functionality and thereby leading to limited applications thereof in making low value items such as paver blocks and brick materials only.        
The main object of the present invention is therefore to provide functionalized brine sludge composites useful for multifarious applications.
Another object of the present invention is to provide a process for the preparation of functionalized brine sludge composites by simultaneous in-situ synthesis of materials inherently present in brine sludge.
Yet another object of the present invention is to provide a process which converts micron sized brine sludge to nano sized brine sludge based materials.
Still another object of the present invention is to provide a process for the preparation of non-toxic functionalized brine sludge based composite materials which have increased homogeneity among the various constituents present therein.
Yet another object of the present invention is to provide a process which utilizes irradiation capability of microwave so as to enable simultaneous and synergistic chemical reactions among the various ions of the reactants, namely brine sludge, fly ash, sodium hydroxide, ethylene glycol, cetyl trimethyl ammonium bromide, and water leading to multifunctional ability of the developed materials.
Still another object of the present invention is to provide a process which ensures total utilization of toxic brine sludge thereby solving the problem associated with disposal thereof.
Yet another object of the present invention is to provide a process which exhibits marked reduction in steps, duration and temperature of synthesis thereby leading to increased productivity.